/**
 * Created by Administrator on 2016/12/30.
 */
function randomNum(min,max){
    return Math.floor(Math.random()*(max-min)+min);
}
function randomColor(min,max){
    var _r = randomNum(min,max);
    var _g = randomNum(min,max);
    var _b = randomNum(min,max);
    return "rgb("+_r+","+_g+","+_b+")";
}
function drawPic(eleId,type){
    var $canvas = document.getElementById(eleId);
    //type 1或null 所有
    //type 2 字母
    //type 3 数字
    var _str =(type==1||type==null)? "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789":
        type==2?"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz":type==3?'0123456789':'';
    var _picTxt = "";
    var _num = 4;
    var _width = $canvas.width;
    var _height = $canvas.height;
    var ctx = $canvas.getContext("2d");
    ctx.textBaseline = "bottom";
    ctx.fillStyle = randomColor(180,240);
    ctx.fillRect(0,0,_width,_height);
    for(var i=0; i<_num; i++){
        var x = (_width-10)/_num*i+10;
        var y = randomNum(_height/1.5,_height);//调位置
        var deg = randomNum(-45,45);
        var txt = _str[randomNum(0,_str.length)];
        _picTxt += txt;
        ctx.fillStyle = randomColor(10,100);
        ctx.font = randomNum(36,40)+"px SimHei";
        ctx.translate(x,y);
        ctx.rotate(deg*Math.PI/180);
        ctx.fillText(txt, 0,0);
        ctx.rotate(-deg*Math.PI/180);
        ctx.translate(-x,-y);
    }
    for(var i=0; i<_num; i++){
        ctx.strokeStyle = randomColor(90,180);
        ctx.beginPath();
        ctx.moveTo(randomNum(0,_width), randomNum(0,_height));
        ctx.lineTo(randomNum(0,_width), randomNum(0,_height));
        ctx.stroke();
    }
    for(var i=0; i<_num*10; i++){
        ctx.fillStyle = randomColor(0,255);
        ctx.beginPath();
        ctx.arc(randomNum(0,_width),randomNum(0,_height), 1, 0, 2*Math.PI);
        ctx.fill();
    }
    return _picTxt;
}